The present invention relates to a portable power working machine such as a chain saw, a power cutter, a hedge trimmer, etc., which is provided with an internal combustion engine as a driving power source for driving the working components thereof, and in particular, to a portable power working machine which is designed to prevent, in a most possible manner, an air cleaner attached to an air intake system of an internal combustion engine from being clogged with dust and to make it possible to effectively improve the performance thereof to cool the internal combustion engine.
A conventional portable power working machine, such as a chain saw, is generally constructed such that a small air-cooled internal combustion engine acting as a driving power source for driving the working components, such as a saw chain, is mounted in a main housing, that a cooling fan driven by the internal combustion engine is disposed on one side of the main housing, that the air introduced into the main housing by means of the cooling fan is forced to blow against the internal combustion engine (the cylinder portion thereof) and that external air is permitted to enter, through an air cleaner, a carburetor chamber and a carburetor, into the internal combustion engine.
One of important problems in the portable power working machine which is constructed as mentioned above is how to effectively cool the internal combustion engine by the air that has been sucked by means of the cooling fan into the main housing.
Additionally, in the operation of this portable power working machine, dust that includes sawdust of relatively large size, powder of cut material and sand-like dust is inevitably generated. When dust of those kinds is allowed to enter together with air into the air intake system of the internal combustion engine, and to collect on the filter element of the air cleaner, the clogging of the filter will be resulted, thus giving rise to an irregularity of the internal combustion engine as well as a deterioration of performance of the internal combustion engine due to an insufficiency in the flow speed of intake air. Accordingly, it is required in the operation of the portable power working machine to usually clean the air cleaner, etc., which is a task that is quite troublesome for the operator.
The present invention has been made to solve the aforementioned problem. In particular, it is an object of the present invention to provide a portable power working machine which is capable of effectively improving the performance thereof to cool the internal combustion engine mounted thereon as a power source for driving the working components thereof, and also capable of preventing, in a most possible manner, an air cleaner of the air intake system of a small air-cooled internal combustion engine from being clogged with dust.
With a view to attaining the aforementioned objects, there is provided, in accordance with the present invention, a portable power working machine comprising: a main housing; an air-cooled internal combustion engine received in the main housing with a cylinder thereof being horizontally disposed and a head portion of the cylinder being orientated rearward; a cooling fan which is adapted to be driven by the internal combustion engine and disposed on one side of the main housing; a guiding wall disposed on one side of the main housing and at a location rear to the cooling fan and projected inward therefrom for guiding cooling air toward the cylinder; an intake passageway formed at a location rear to the cooling fan for introducing air into an air-intake system of the internal combustion engine; and an air-intake port for the intake passageway, the air-intake port being positioned in the vicinity of a root portion of the rear face of the guiding wall.
Preferably, the guiding wall is formed on a fan cover which is disposed inner than an outer cover of the main housing.
In a preferable embodiment, the intake passageway is constituted by the outer cover and the fan cover, and the air-intake port is formed in the fan cover.
Preferably, an upstream end portion of the intake passageway is positioned in the vicinity of bottom of the main housing, and the air-intake port is formed in the vicinity of the upstream end portion to communicate with the intake passageway.
In another preferable embodiment, the air entering from the air-intake port is enabled to enter into a carburetor through the intake passageway and an air cleaner.
Preferably, the air cleaner is formed of a cap-like configuration and detachably secured to a rear end portion of the main housing with a filter member being interposed therebetween as a partitioning wall, thereby enabling the air cleaner to communicate through the filter member with the carburetor.
A typical example of a portable power working machine in which the present invention is especially advantageous is a chain saw which is provided with a saw chain set composed of a saw chain and a guide bar and disposed on the other side of the main housing which is opposite to the aforementioned one side, the chain saw being known to produce large quantities of dust, including relatively large particles during the operation thereof.
According to the aforementioned preferred embodiment of the portable power working machine constructed as described above, the external air that has been introduced into the main housing by means of the cooling fan can be reliably guided toward the cylinder where cooling is most needed by the effect of the guiding wall formed on the fan cover, the air being subsequently employed for cooling the cylinder and then discharged through a discharger port formed in the main housing toward the external atmosphere. Part of the air introduced into the main housing is permitted to enter into the internal combustion engine through the intake passageway, the air cleaner, the carburetor chamber and the carburetor.
In this case, even if large quantities of dust is mixed into the air to be sucked by means of the cooling fan into the main housing, since this air mixed with dust can be concentratedly guided toward the cylinder by the effect of the guiding wall, most of the dust can be prevented from flowing down to the vicinity of the root portion of the rear face of guiding wall (a region where the fan cover is disposed). Therefore, the air that will be introduced, via the intake passageway and the air cleaner, into the carburetor after being sucked from the air-intake port positioned in the vicinity of root portion of the rear face of the guiding wall will be almost free from any dust.
Therefore, accordingly to the portable power working machine of the present invention, since it is constructed such that a guiding wall is formed to thereby enable an air-intake port to be positioned in the vicinity of root portion of the rear face of the guiding wall, the performance thereof to cool the internal combustion engine can be effectively enhanced and, the clogging of the air cleaner of the air intake system of internal combustion engine due to the dust in the sucked air can be minimized, thus making usual cleaning of the air cleaner unnecessary.